1. Field of the Invention
This invention relates to a pneumatic tool, and more particularly to a switch mechanism for a pneumatic tool.
2. Description of the Prior Arts
All pneumatic tools are equipped with a switch mechanism that is actuated by trigger to allow the air enter the inside of the pneumatic tool to perform pneumatic operation. The switch mechanism is an indispensable part of the pneumatic tool, which has many different structural forms. The motivation of the present invention is to develop a switch mechanism that will not damage the base body of the pneumatic tool, and part of the switch mechanism is easy to be replaced after it is worn or broken.
As shown in FIGS. 1 and 2, a conventional switch mechanism for a pneumatic tool generally includes a choke ring 12, a control rod 13 and a choke member 14. The choke ring 12 is fixed in an air passage 11 of a base body 10 of the pneumatic tool, and an air hole 121 is formed at the center of the choke ring 12. The control rod 13 is swayably inserted through the air hole 121 of the choke ring 12 with a first end of the control rod 13 corresponds to a trigger 15 of the pneumatic tool and a first end of which is inserted in a choke member 14. The choke member 14 is provided around the outer periphery thereof with a choke portion 141 that is pushed by a spring 16 and to seal the choke ring 12. When the pneumatic tool is in use, the choke portion 141 of the choke member 14 is pushed by the spring 16 to seal the air hole 121 of the choke ring 12, so that the air in the air passage 11 of the base body 10 is unable to enter the inside of the base boy via the air hole 121 of the choke ring 12. As shown in FIG. 3, if the user presses the trigger 15, the control rod 13 will be pushed by the trigger 15 to sway an angle and the choke portion 141 of the choke member 1 will disengage from the air hole 121 of the choke ring 12. At this moment, air is allowed to enter the base body through the air hole 121 of the choke ring 12. This conventional switch mechanism still has some disadvantages that are explained as follows:
First, in operation, the trigger 15 pushes the control rod 13 to make it sway an angle and synchronously make the choke member 14 sway an angle too. Since there is no any component arranged between the choke member 14 and the choke ring 12, and between the choke member 14 and the inner wall of the air passage 11 of the base body 10. The choke portion 141 of the choke member 14 directly contacts the choke ring 12 and the air passage 11 of the base body 10. After a certain time of use, the choke ring 12 and the inner wall of the air passage 11 of the base body 10 will be worn or broken due to different hardness of the respective components.
Second, once the choke ring 12 is worn or broken, not only the choke ring 12 and the choke member 14 will lose their air-tightness, but also the choke ring 12 will be difficult to be replaced since it is preset in the air passage 11 of the base body 10.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional switch of a pneumatic tool.